Cleaning liquid purification device for use in wet-type electrostatic photography

ABSTRACT

A cleaning liquid purification device for use in wet-type electrostatic photography. A container having cleaning fluid therein acts as a first electrode. An adjacent container having developing liquid therein acts as an opposing electrode, and an endless belt passing therebetween has the same polarity as the developing liquid container. Passage of the belt pricks up excess toner form the cleaning liquid container for dispersal in the developing liquid container.

3,790,466 CLEANING LIQUID PURIFICATION DEVICE FOR USE IN w ET-TYPE HIDEAKI AKIYAMA ELECTROSTATIC PHOTOGRAPHY Filed May 16, 1969 F l G.

FIG. 2

FIG. 3

Feb. 5, 1974 IN V EN TOR. H/DEA K/ AK/ YA NA United States Patent US. Cl. 204-300 3 Claims ABSTRACT OF THE DISCLOSURE A cleaning liquid purification device for use in wettype electrostatic photography. A container having cleaning fluid therein acts as a first electrode. An adjacent container having developing liquid therein acts as an opposing electrode, and an endless belt passing therebetween has the same polarity as the developing liquid container. Passage of the belt picks up excess toner from. the cleaning liquid container for dispersal in the developing liquid container.

BACKGROUND OF THE INVENTION The present invention relates to a cleaning liquid purification device therefor for use in electrostatic photography, especially wet-type electrostatic photography.

In electrostatic photography, a light sensitized sheet consisting of an electrically insulating support or substrate applied with a layer of a photoconductor such as special zinc oxide in a binder is exposed to form an electrostatic latent image due to photoelectric emission (noncharge electrostatic photography). Alternatively, said sensitized sheet is applied with the corona discharge generated at a position spaced apart from the sensitized sheet so that the weak electrostatic charge may be imparted thereto. Thereafter, the light sensitized sheet is exposed, thereby forming an electrostatic latent image (weak charge electrostatic photography). In both of the above described photographic methods, toner is used for developing the electrostatic latent image into a visible image. The developing liquid consists of a carrier and a resinous pigment. For example, a developing liquid may be prepared by suspending resin coated carbon black in a carrier having a high electric resistance. The sensitized sheet bearing thereupon the electrostatic latent image is immersed in this developing solution. This is called wettype electrostatic photography. In this case, the potential of the electrostatic charge forming an electrostatic latent image is very low so that a highly sensitized and high toner concentration developing liquid containing toner having a very small particle size is used in order to efficiently obtain a good quality developed image. When the exposed sensitized sheet is developed by such developing liquid, excess toner is attracted upon the sensitized sheet in addition to toner required for forming a visible image. This excess toner must be removed in order to improve the image quality, for example by washing the developed sensitized sheet in a cleaning liquid having a high electric resistance such as a carrier of the developing liquid. This cleaning liquid is repetitively used so that the toner concentration in the cleaning liquid is increased finally to such an extent that the cleaning efiect of the cleaning liquid is lost. On the other hand, it is very uneconomical to discharge the used cleaning liquid for such operation.

However, no satisfactory cleaning liquid treatment method and a device therefor has not been proposed.

3,790,466 Patented Feb. 5, 1974 One of the objects of the present invention is therefore to provide a device for permitting the repetitive use of a cleaning liquid without discharging it for each cleaning operation, by recovering toner from the cleaning liquid.

Another object of the present invention is to provide a cleaning liquid purification device in which purification of cleaning liquid may be effected continuously and automatically.

A further object of the present invention is to provide a cleaning liquid purification device for discharging the toner removed or recovered from the cleaning liquid to a predetermined place.

A still another object of the present invention is to provide a cleaning liquid purification device for discharging the toner recovered from the cleaning liquid into a developing liquid.

SUMMARY OF THE INVENTION In brief, the present invention provides a device for purification of a cleaning liquid for wet-type electrostatic photography in which at least a pair of electrodes are disposed in such a manner that at least one of said pair of electrodes may contact with the cleaning liquid; and a voltage is applied across said pair of electrodes so that said one of said pair of electrodes attracts the toner in the cleaning liquid, thereby removing the toner from the cleaning liquid.

According to one embodiment of the present invention, said pair of electrodes consist of grid-like electrode plates.

According to another embodiment of the present invention, a container receiving therein the cleaning liquid serves as one of the pair of electrodes. In this arrangement, only one electrode may be provided; and all of the toner in the cleaning liquid is imparted with electrophoretic mobility or migration so that all of the cleaning liquid may be uniformly cleaned regardless of its position in the container.

According to a further embodiment of the present invention, one of said pair of electrodes is comprised of a roller one portion of which is immersed in the cleaning liquid. This arrangement facilitates the automatic collection of the attracted toner at a predetermined place.

According to a yet another embodiment of the present invention, one of said pair of electrodes is comprised of an electrode conveyer belt. This arrangement permits the automatic transportation of the attracted toner to a predetermined place, for example into the developing liquid so that not only the cleaning liquid may be purified or freed from the toner but also the concentration of the developing liquid may be maintained substantially at a predetermined level.

According to a yet further embodiment of the present invention, [fin-shaped electrode members are disposed in closely spaced-apart relation with the opposing electrode and applied with the polarity opposite to that of said opposing electrode. This arrangement will increase the electrophoretic mobility of the toner in the cleaning liquid because the electrodes are closely spaced apart from each other.

The above and other objects, features and advantages of the present invention will become more apparent from the following description with reference to the accompanying drawings.

of one embodiment of a cleaning liquid purification device;

FIG. 2 is a perspective view with a part broken away of another embodiment of a cleaning liquid purification device; and

FIG. 3 is also a perspective view with a part broken away of still another embodiment of a cleaning liquid purification device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, within a cleaning liquid container 1 containing a cleaning liquid are disposed grid-like electrode plates 2 and 3 spaced apart from each other by insulating support members or separators 4. When these electrode plates 2 and 3 are energized and a developed copy sheet is washed in the cleaning liquid above the electrode plates, the toner is freed from the copy sheet and directed toward one electrode plate, for example 3, having the polarity opposite to that of the electrostatic charge imparted to the toner. Thus, the toner is always attracted by the electrode plate 3, which may be removed away from the cleaning liquid container at a suitable time so as to scrape the deposited toner off from the electrode plate 3. Alternatively, the voltage applied to the electrode plates may change its polarities. The recovered toner may be returned to a developing liquid and used again. The electrode plate may have other configurations such as net, rod, bar, etc. other than grid.

Referring to FIG. 2, within a cleaning liquid container 21 is disposed rotatably an electrode roller 22, which is electrically insulated from the container 21 so that they form a pair of opposed electrodes. A brush-like member 22a is normally disposed in sliding contact relation with the roller 22 so that it is applied with a voltage having the polarity opposite to that of the electrostatic charge imparted to the toner. A toner receiving vat 23 is disposed within the cleaning liquid container 21 in such a manner that one lateral side edge 23a of the vat 23 is normally in contact with the peripheral surface of the electrode roller 22. Thus, when a developed copy sheet is washed in the cleaning liquid, excess toner attached to the copy sheet is washed olf therefrom and attached to the roller 22. When the roller 22 is rotated, the toner deposited upon the peripheral surface of the roller 22 is scraped 01? by said side edge 23a of the vat and received therein. The roller 22 may be continuously rotated by suitable drive means (not shown) and the toner received in the vat 23 may be returned to the developing liquid at a suitable time interval.

Referring to FIG. 3, a pair of developing liquid and cleaning liquid containers 31 and 32 are disposed in sideby-side relation and electrically insulated from each other by an insulating member 33. This pair of containers 31 and 32 form a pair of electrodes. Insulating rollers 34 and 35 having a relatively large diameter are rotatably disposed in the containers 31 and 32 respectively. Pairs of (guide) rollers 36 and 37; 38 and 39 having a diameter smaller than that of the roller 34 or 35 are rotatably disposed upwardly of the rollers 34 and 35 respectively. Over the above described rollers, 34, 35, 36, 37, 38 and 39 is lapped an electrode belt 40 formed of for example a metallic foil or sheet. A brush-like member 41 is disposed in normally sliding contact with the electrode belt 40. When the rollers 34 and 35 are rotated by suitable drive means not shown, the belt 40 is moved in the direction indicated by the arrow. In this case, a potential having a polarity opposite to that of the electrostatic charge imparted to the toner in the cleaning liquid is applied to the container 31 while the container 32 is applied with a voltage having the same polarity with that of the toner. The electrode belt 40 is applied with a voltage which has the same polarity with that of the container 31 but is lower than the latter. Therefore, the excess toner washed olt from the developed copy sheet in the cleaning liquid is attracted toward and deposited upon the belt 40. The toner upon the belt 40 is transferred into the developing liquid in the container 31 and then is dispersed therein. In order to facilitate the electrophoretic movement of the toner, electrode fins 42 and 43 the ends of which are securely fixed to the bottoms of the containers 31 and 32 respectively are extending in closely spaced apart relation with the peripheral surfaces of the rollers 34 and 35 respectively. The material for the electrode belt 40 may be a flexible conductive material and of any configuration.

What is claimed is:

1. A cleaning liquid purification device for wet-type electrostatic photography comprising first electrode means in the form of a cleaning liquid container adapted to hold liquid having excess toner therein and adapted to be provided with a predeterrnined polarity from a predetermined voltage applied thereto;

second electrode means in the form of a developing liquid container adapted to have a voltage applied of opposite polarity with respect to said first electrode means, said developing liquid container disposed closely adjacent to said cleaning liquid container and electrically insulated therefrom;

a pair of insulating rollers each disposed respectively in one of said containers and adapted to be immersed in the liquid therein;

said second electrode means including a belt movable around each of said rollers; and

said belt being an endless belt adapted to pass through said cleaning liquid to attract toner thereon which is transferred and dispersed therefrom into the developing liquid as said belt subsequently passes therethrough.

2. A cleaning liquid purification device according to claim 1 in which said belt is adapted to have a voltage applied thereto of the same polarity but of a value less than the voltage applied to said developing liquid container.

3. A cleaning liquid purification device according to claim 1 in which a pair of groups each comprising a plurality of fins are adapted to be immersed respectively in said liquid containers to extend in closely spaced relation with respect to a respective roller, each group of fins having a polarity opposite to that of the container in which it is immersed.

References Cited UNITED STATES PATENTS 1,590,601 6/ 1926 Taylor 204-300 X 2,485,335 10/1949 Tyson 204-300 X 2,900,320 8/1959 Metcalfe et al. 204-180 X 2,944,952 7/ 1960 McMinn, Jr. 204-4300 X 3,396,097 8/1968 Wolcott 204--300 3,436,326 4/ 1969 Stober 204l 3,440,160 4/ 1969 Matkovich 204- GERALD L. KAPLAN, Primary Examiner A. C. PRESCOTT, Assistant Examiner 

